Sky and Telescope - May 2018 - 35

N ASA / JPL- CA LTEC H / M S S S / DA MI A BO U IC

My favorite example of this contrast
likely to ﬁnd obscure images. Even images
Anybody who digs
comes
from Viking. A friend in the imageor observations that are familiar can often
into the data stored
processing enthusiast community, Ted
be processed differently, to emphasize
in the PDS is likely to Stryk, shared a photo he had processed
features hidden in shadow or washed out
find obscure images.
from data returned to Earth by the Soviet
by bright light. There are many ways to
Union's ill-fated Mars 3 mission. It shows
approach data.
Even images or
Consider the Cassini image sequence
observations that are a crescent-phase Mars that looks almost
Titan because its surface is hidden
that unequivocally proved the existence
familiar can often be like
from view behind a global dust storm.
of south-polar plumes at Enceladus. The
processed differently, When I shared it on Twitter, I remarked
mission chose to release a long-exposure
that it was the ﬁrst time I'd seen such a
photo, in which the crescent of Enceladus
to emphasize
high-phase photo of Mars (except from
is saturated and the individual jets make
features hidden in
the VMC camera on Mars Express).
obvious pointed spikes. From the same
shadow or washed
Someone responded to correct me,
sequence, I found a shorter-exposure
out by bright light.
mentioning a similar-phase image
image, in which surface detail in the
taken as one of the twin Viking orbiters
sunlit crescent is visible, while the plumes
approached the planet in 1976. I Googled for it and found
appear as a subtle mist against the background sky (seen on
an astonishingly ugly image on a NASA website. Sure that I
page 30). Neither is better; they're different photos, each
could do a better job, I went digging into the Imaging Node
worth appreciating.
in search of Viking's Mars approach images. I found not just
Once you've learned how to work with the relatively
one, but six breathtaking color crescent-phase photos of the
straightforward Cassini data, it's even more rewarding to
planet, data that had been waiting all this time for me to
turn your attention to earlier missions, particularly the ones
brush off the dust, polish it, and put it on display for all to
from the 1970s. Those data sets are more difﬁcult to work
see. Many more such treasures await the brave explorers who
with: more distortion, more blur, less bit-depth, less docusearch for them. I encourage all of you to try!
mentation, and on and on. But there is a huge difference
between what 1970s spacecraft engineers could achieve in
image processing when those missions were active and what
¢ Contributing Editor EMILY LAKDAWALLA blogs for the Plana self-educated 21st-century space fan with a garden-variety
etary Society at planetary.org/blogs and frequently hunts for
personal computer can achieve now.
overlooked gems in the PDS.

s k y a n d t e l e s c o p e . c o m * M AY 2 0 1 8

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Sky and Telescope - May 2018

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